Flangeless electromagnetic flowmeter

ABSTRACT

A flangeless electromagnetic flowmeter insertable between upstream and downstream pipes which have the same internal diameter, the adjacent ends of said pipes having like flanges. The cylindrical body of the flowmeter is interposed between the flanged ends of the pipes, the body being provided with an annular pressure vessel formed of insulating material to define a central flow passage whose diameter matches the internal diameter of the pipe whereby the flowmeter functions to meter the flow rate of fluid passing through the pipes and the passage along a longitudinal axis extending therethrough. A pair of electromagnetic coils is embedded in the vessel at opposed positions with respect to the passage to establish a magnetic field therein whose lines of flux are substantially perpendicular to the longitudinal axis. Also embedded in the vessel is a pair of electrodes at opposed positions with respect to the passage, the electrodes lying along a transverse axis at right angles both to the lines of flux and the longitudinal axis. The flanged ends of the pipe are bridged by bolts to clamp the flowmeter body therebetween.

RELATED APPLICATION

This application is a division of the copending application Ser. No.811,276, filed June 29, 1977, which in turn is a division of anapplication that is now U.S. Pat. No. 4,098,118.

BACKGROUND OF INVENTION

This invention relates generally to electromagnetic flowmeters, and moreparticularly to a flangeless flowmeter whose components are integratedto form a highly compact, low-cost unit that may be readily installed ina flow line.

Magnetic flowmeters such as those disclosed in U.S. Pat. Nos. 3,695,104;3,824,856; 3,783,687 and 3,965,738, are especially adapted to measurethe volumetric flow rates of fluids which present difficult handlingproblems, such as corrosive acids, sewage and slurries. Because theinstrument is free of flow obstructions, it does not tend to plug orfoul. The flowmeter can be used to meter liquids without regard toheterogenous consistency.

An added advantage of an obstructionless construction is that pressurelosses are reduced to levels encountered in equivalent lengths of equaldiameter pipeline, thereby reducing or conserving pressure sourcerequirements in new or existing hydraulic lines as compared to othermetering techniques.

In a magnetic flowmeter, an electromagnetic field is generated whoselines of flux are mutually perpendicular to the longitudinal axis of theflow tube through which the fluid to be metered is conducted and to thetransverse axis along which the electrodes are located atdiametrically-opposed positions with respect to the tube. The operatingprinciples are based on Faraday's law of induction, which states thatthe voltage induced across any conductor as it moves at right anglesthrough a magnetic field will be proportional to the velocity of thatconductor. The metered fluid effectively constitutes a series of fluidconductors moving through the magnetic field; the more rapid the rate offlow, the greater the instantaneous value of the voltage established atthe electrodes.

Typical of commercially-available electromagnetic flowmeters is thatunit manufactured by Fischer & Porter Co. of Warminster, Pa., whoseModel 10D1430 flowmeter is described in Instruction Bulletin10D1430A-1-Revision 4. This meter consists of a carbon-steel pipe spoolflanged at both ends and serving as a meter body. Saddle-shaped magneticcoils are fitted on opposite sides of the inner surface of the meterbody, the magnetically-permeable pipe spool acting as a core or returnpath for the magnetic field generated by these coils.

The coils in this known form of meter are potted within an epoxy-basedcompound. An interior liner of neoprene or similar insulating materialis inserted within the pipe and turned out against the faces of themounting flanges. Disposed at diametrically-opposed positions within thecentral portion of the meter body are two cylindrical electrodes thatare insulated from the pipe, the faces of the electrodes being flushwith the inner surface of the pipe and coming in contact with the fluidto be metered. Connected to these electrodes and housed in a boxexternal to the pipe are calibration components and a pre-amplifier.

In installing a standard magnetic flowmeter of the above-described type,the meter is interposed between the upstream and downstream pipes of afluid line, each pipe having an end flange. The mounting flanges on themeter are bolted to the flanges of line pipes. It is, of course,essential that the circle of bolt holes on the mounting flanges of themeter match those on the pipe flanges.

In a magnetic flowmeter, the flow tube is subjected to the same fluidpressure as the line pipes. The flow tube must therefore be of amaterial and of a thickness sufficient to withstand this pressure, eventhough the strength of the flow tube is unrelated to its measuringfunction. This design factor contributes significantly to the cost of astandard meter. Existing meters of the above-described type which aremade up of components that must be assembled are generally ofsubstantial size and weight and quite expensive to manufacture.

SUMMARY OF THE INVENTION

In view of the foregoing, it is the primary object of this invention toprovide a compact and readily installable electromagnetic flowmeterwhose weight and dimensions are substantially smaller than existingtypes of meters.

Among the significant features of a magnetic flowmeter in accordancewith this invention is that despite its reduced volume and weight, it iscapable of withstanding high fluid pressures and operates efficientlyand reliably to accurately measure flow rates.

Moreover, a flowmeter in accordance with the invention is much lesscostly to produce than existing types. Indeed, while known types ofmeters cost hundreds of dollars to produce, a flowmeter in accordancewith the invention can be manufactured for under a hundred dollars atcurrent labor and material costs, thereby making it possible to usethese flowmeters in many industrial applications in which theinstallation of existing types is precluded because of their high cost.

More particularly, it is an object of this invention to provide aminiature magnetic flowmeter which includes a ferromagnetic ring servingas a mold within which is formed an annular pressure vessel of highstrength insulating material that encapsulates the electromagnetic fieldcoils and the electrodes of the unit, the pressure vessel having acentral passage through which the fluid to be metered is conducted,whereby the molding ring functions not only as a magnetic return pathfor the coils but also as a structural reinforcement for the pressurevessel molded therein.

Briefly stated, these objects are attained in a flangeless meterinterposable between the flanged ends of upstream and downstream linepipes for metering fluid passing through the line.

The meter is constituted by a ferromagnetic ring within which a pair ofelectromagnet coils is supported at opposed positions along adiametrical axis normal to the longitudinal axis of the ring, thelongitudinal axis passing through the central flow passage of an annularpressure vessel which is formed of high strength insulating material andis molded within the ring to encapsulate the coils as well as a pair ofelectrodes disposed at diametrically-opposed positions with respect tothe passage along a transverse axis at right angles to the coil axis todefine a unitary structure.

The unit is compressible between the end flanges of the pipes bybringing bolts that pass through bore holes in the pressure vessel orlie outside of the ring to encage the unit.

OUTLINE OF THE DRAWINGS

For a better understanding of the invention as well as other objects andfurther features thereof, reference is made to the following detaileddescription to be read in conjunction with the accompanying drawings,wherein:

FIG. 1 is a perspective view of a first embodiment of an electromagneticflowmeter of the ring type in accordance with the invention, theinternal components being shown in dotted lines;

FIG. 1A is the same as FIG. 1, except that a sector of the structure iscut away to expose some of the internal components;

FIG. 1B illustrates, in section, the molding arrangement for fabricatingthe meter shown in FIG. 1;

FIG. 2 is a perspective view of a second embodiment of anelectromagnetic flowmeter of the ring type in accordance with theinvention, this structure differing from that in FIG. 1 only in that itlacks a central shell;

FIG. 3 is a perspective view of a third embodiment of an electromagneticflowmeter in accordance with the invention, the meter being ringless;

FIG. 3A is a view which is the same as FIG. 3, except that a sector iscut from the structure to expose some of the internal components;

FIG. 3B illustrates in section the molding arrangement for fabricatingthe meter shown in FIG. 3;

FIG. 4 illustrates, in perspective, a fourth embodiment of anelectromagnetic flowmeter in accordance with the invention, the meterbeing of the driven-shield type;

FIG. 4A is the same as FIG. 4, save that a sector of the cylinder hasbeen cut away to expose some of the internal components;

FIG. 4B is a transverse section taken through the meter shown in FIG. 4;

FIG. 5 is a transverse section taken through a fifth embodiment of acylindrical flowmeter of the driven-shield type which differs from thatin FIG. 4 only in that the electrodes are insulated rather than indirect contact with the fluid being metered;

FIG. 6 is a perspective view of a sixth embodiment of a flowmeter inaccordance with the invention in which the preamplifier for theelectrodes is encapsulated in the meter; the structure being cut away toexpose some of the internal components;

FIG. 7 is a perspective view of a seventh embodiment of a magneticflowmeter in accordance with the invention in which the drive circuitfor the electrodes is also encapsulated in the meter;

FIG. 7A is the same as FIG. 7 with the structure cut in half to exposesome of the internal components;

FIG. 7B is a transverse section taken through the meter of FIG. 7;

FIG. 8 illustrates, in perspective, how the meter shown in FIG. 7 isinstalled in a pipe line;

FIG. 9 illustrates how a meter in accordance with the invention havingbore holes therein which register with the flange holes of the linepipes is compressively mounted in the fluid line; and

FIG. 10 illustrates how a meter in accordance with the invention whosebore holes do not register with the flange holes of the line pipes, iscompressively mounted in the fluid line.

DESCRIPTION OF INVENTION First Embodiment

Referring now to FIGS. 1, 1A and 1B, there is shown a preferredembodiment of a flowmeter in accordance with the invention whichincludes a cylindrical ferromagnetic ring 10, preferably machined ofcold rolled steel. Mounted within ring 10 is a pair of electromagnetcoils 11 and 12. These coils occupy opposed positions along adiametrical axis Z which is normal to the longitudinal axis Y of thering.

Coils 11 and 12 are conventional solenoids with a ferromagnetic corethat may also be of cold rolled steel, the cores being bolted or screwedto ring 10 whereby the ring serves to complete a magnetic path betweenthe coils.

Concentrically disposed within ring 10 is a spool-shaped plastic shell13 defining a central flow passage 14 extending along longitudinal axisY. Shell 13 is provided with a front end flange 13A of small diameterwhose face lies in the same plane as the front end of ring 10, and arear end flange 13B whose diameter matches the internal diameter of thering and whose face lies in the same plane as the rear end of the ring.Flange 13B, as best seen in FIG. 1B, is provided with a circular rim 13Cwhich fits within the rear end of the ring to form therewith a moldingcup which is open at the front end.

Shell 13 is provided, at a position midway between its flanges, with apair of internally-threaded tubular sockets 15 and 16 which projectlaterally therefrom at diametrically-opposed positions with respect tocentral flow passage 14. Threadably received within sockets 15 and 16are electrodes 17 and 18 whose faces are flush with the wall of passage14 and therefore make direct contact with the fluid passingtherethrough.

Mounted on rear flange 13B at equi-spaced positions along a circleconcentric with the flange are four tubes, 19, 19A, 20 and 21 whichserve to define a circle of mounting bores. The tubes are preferably ofinsulating Teflon (TFE).

The molding space between ring 10 and shell 13 is filled with a pottingcompound such as an epoxy resin of the reactive type forming a tightcross-linked polymer network characterized by toughness, goodadhesiveness, corrosion and chemical resistance as well as gooddielectric properties. This epoxy compound may be a thermosetting resinbased on the reactivity of the epoxide group or from polyolefinsoxidized with peracetic acid. The resultant body which adheres to ring10 constitutes an annular pressure vessel 22 that encapsulates coils 11and 12 and electrodes 17 and 18 to form an integrated, unitary flowmeterstructure.

Shell 13 is preferably injection molded of KYNAR (polyvinylidenefluoride) which has high tensile and compressive strength, is thermallystable and resistant to acids, alkalies and halogens, thereby making itsuitable for virtually all fluids, however, corrosive, in a very broadtemperature range.

Thus to manufacture the unit, it is only necessary to bolt coils 11 and12 to ring 10, to attach electrodes to shell 13, and to insert the shellin the ring, after which the potting compound is introduced to fill thespaces between the ring and shell and to define the annular pressurevessel 22. The leads (not shown) connected to the coils and to theelectrodes are embedded in the pressure vessel and taken out through anopening 23 in the ring. In practice, to null out noise, each electrodemay be provided with two leads going to a potentiometer, the output ofthe electrodes being taken from the sliders of the two potentiometers.

In operation, the high-strength pressure vessel 22 is subjected to thepressure of the fluid being metered, the fluid passing through passage14 whose diameter matches the internal diameter of the downstream andupstream pipes between which the unit is interposed. The outer ring 10not only serves as the magnetic return path for the electromagnets toproduce an electromagnetic field whose lines of flux are parallel toaxis Z and mutually perpendicular to axes X and Y, but it also acts tostructurally reinforce the pressure vessel, so that the unit is capableof withstanding exceptionally high fluid pressures.

The nature of the unit is such that it lends itself to miniatureflowmeter sizes in the range of from 0.1" to 2" as well as for 3" to 4"sizes. Tubes 19, 20 and 21 need not be a permanent part of the unit, andrelease agents may be provided therewith, making it possible to removethese tubes after the pressure vessel is molded, so that the mountingbores are then formed directly in the vessel.

The manner in which the unit may be installed is shown in FIGS. 9 and10. In FIG. 9, the upstream and downstream pipes 24 and 25 are providedwith end flanges 24A and 25A, respectively, each having a circle of boltholes which register with the bores in tubes 19, 20 and 21 of the unit.Bridging the flanges 24A and 25A are three bolts 26 which pass throughtubes 19, 20 and 21 and serve to compress the flowmeter unit between thepipe flanges. In practice, gaskets may be placed at the ends of theunits to insure an effective seal to prevent fluid leakage.

It is not essential, however, that the upstream and downstream pipeshave flanges with bores which match those in the unit. Thus, as shown inFIG. 10, the upstream and downstream pipes 27 and 28 have flanges 27Aand 28A whose bores are outside the circumference of ring 10. Bolts 26in this instance act to encage the unit as well as to subject it tocompression between the pipe flanges.

Second Embodiment

This embodiment, as shown in FIG. 2, is identical to that of FIG. 1,except that in place of a flanged plastic shell 13 which forms apermanent part of the unit, use is made of a removable core (not shown)which serves to define with ring 10 the mold for the potting compoundthat encapsulates coils 11 and 12 and electrodes 17 and 18 and definesthe annular pressure vessel 22. But upon completion of the moldingoperation, the core is removed to form a flow passage 14 directly in thepressure vessel, not in the shell. This unit may be mounted in the samemanner as the first unit.

Third Embodiment

In the embodiment illustrated in FIGS. 3, 3A and 3B, instead of an outersteel ring as in the first and second embodiments, plastic shell 29,which is similar to that of shell 13 in FIG. 1 and is injection moldedof the same material (KYNAR), is surrounded and reinforced by ahigh-strength non-magnetic spool 30 such as non-magnetic steel, brass orplastic material whose front and rear flanges 30A and 30B conform to andback up the front and rear flanges 29A and 29B of the shell. Electrodes17 and 18 are molded into the shell within sockets 15 and 16 whichproject through openings in the spool.

Since there is no ring, the magnetic return path in this instance isprovided by ferromagnetic straps 31 which interconnect the cores ofelectromagnet coils 11 and 12.

Electrodes 17 and 18 and coils 11 and 12 are encapsulated in a moldedpressure vessel 32 which is formed by a potting compound of the typepreviously described. However, in this instance, in lieu of aferromagnetic ring which forms the mold in conjunction with the plasticshell and becomes a permanent structural component of the unit, use ismade of a releasable molding ring of plastic or other suitable material.Then when the pressure vessel is completed and the ring is removed, theouter surface of the unit is that of the pressure vessel 32.

Fourth Embodiment

Flowmeters are known, such as those disclosed in U.S. Pat. No. 3,174,831and in the copending application of Appel, Ser. No. 617,982, filed Sept.29, 1975, now U.S. Pat. No. 3,999,443, in which a meter energized by ana-c field is provided with a pair of planar detection electrodes oflarge area and a driven shielding electrode of even larger areacooperating with each detector electrode.

For measuring dielectric fluids, the electrodes are covered by thedielectric lining of the flow tube and are thereby protected from thefluid. This lining, together with the dielectric of the fluid,constitutes the dielectric of a capacitor whose plates are formed by theplanar measuring electrodes.

In the embodiment illustrated in FIGS. 4, 4A and 4B, the molded annularpressure vessel 33 has embedded therein a pair of planar detectorelectrodes 34 and 35 which are curved to conform to the central passage36 running through the pressure vessel. Also embedded in the pottingcompound behind the detector electrodes are a pair of shieldingelectrodes 37 and 38 which are larger in area than the detectorelectrodes but with a concentric curvature. Leads 39 and 40 for thedetector electrodes are the inner conductors of coaxial lines whoseouter conductors 41 and 42 are connected to the shielding electrodes.

Electromagnet coils 43 and 44 for this circuit have a rectangularcross-section with a rectangular core rather than the usual cylindricalsolenoid form. The purpose of this rectangular structure is to establishan electromagnetic field whose lines of flux which intersect thelongitudinal flow axis are operative within the wide region covered bythe broad area of the electrodes. In this embodiment, detectingelectrodes 34 and 35 are exposed to and in direct contact with the fluidpassing through passage 36.

Coils 43 and 44 are bolted to a ferromagnetic outer ring 45 which servesboth as the magnetic return path and as the reinforcement for pressurevessel 33. In this instance, it will be seen that foursymmetrically-arranged bore holes 46, 47, 48 and 49 are provided tocompressively mount the unit between the end flanges of the line pipes.

Fifth Embodiment

The flowmeter arrangement illustrated in FIG. 5 is identical to that inFIG. 4 and includes planar detecting electrodes 34 and 35 and planarshielding electrodes 37 and 38, except that in this instance electrodes34 and 35 are displaced inwardly from the wall of passage 36 and areinsulated from the fluid by the dielectric material of pressure vessel50.

Sixth Embodiment

The arrangement in FIG. 6 is essentially the same as that in FIG. 4 withplanar detecting electrodes 34 and 35 and planar shielding electrodes 37and 38. However, in this instance, instead of extending leads from theseelectrodes to a preamplifier external to the unit, as is the usualpractice, the preamplifier components are mounted on a printed circuitstrip 51 which is joined to shielding electrode 38 and is embedded inpressure vessel 33.

By so embedding the preamplifier in the unit, one not only avoids theneed for an external box to house the preamplifier, but microphonics andother noises resulting from an externally-mounted amplifier are avoided,for the preamplifier's position is stable and the circuits thereof areshielded by ring 10.

Seventh Embodiment

In the magnetic flowmeter disclosed in the Mannherz et al. U.S. Pat. No.3,783,687, whose entire disclosure is incorporated herein by reference,the electromagnet coils are driven by a low-frequency square waveproduced by applying the output voltage of an unfiltered full-waverectifier to the coils and periodically reversing the voltage polarityat a low-frequency rate by means of an electronic switch. The outputfrom the detecting electrodes is fed to an a-c preamplifier.

The embodiment shown in FIG. 7 is identical to that in FIG. 6; but inaddition to embedding a preamplifier 51 in the pressure vessel, a drivecircuit 52 of the type disclosed in the Mannherz et al. patent is alsoembedded therein. Drive circuit 52 is initially supported from a curvedprinted circuit strip 53 mounted on the rear of shielding electrode 38.

FIG. 8 illustrates the manner in which this unit is compression mountedbetween flanges 54A and 55A of line pipes 54 and 55 by bridging bolts 56which act to encage the unit. Hence no use is made in this mounting ofthe bore holes in the pressure vessel.

While there have been shown and described preferred embodiments of aunitary electromagnetic flowmeter in accordance with the invention, itwill be appreciated that many changes and modifications may be madetherein without, however, departing from the essential spirit thereof.

I claim:
 1. A flangeless electromagnetic flowmeter insertable betweenupstream and downstream pipes which have the same internal diameter, theadjacent ends of said pipes having like annular flanges, each providedwith a like series of holes which lie in a circle, said flowmetercomprising:A a cylindrical flowmeter body interposed between the flangedends of the pipes, said body being provided with an annular pressurevessel formed of insulating material to define a central flow passagehaving a diameter matching the internal diameter of the pipe whereby theflowmeter functions to meter the flow rate of fluid passing through saidpipes and said passage along a longitudinal axis extending therethrough;B a pair of cylindrical electromagnetic coils embedded in saidinsulating material at diametrically-opposed positions with respect tosaid passage to establish a magnetic field therein whose lines of fluxare substantially perpendicular to said longitudinal axis; C a pair ofelectrodes embedded in said insulating material at opposed positionswith respect to said passage, said electrodes lying along a transverseaxis at right angles both to said lines of flux and said longitudinalaxis; said insulating material having bores extending longitudinallytherethrough which lie on a circle concentric with said central flowpassage and which avoid said coils and said electrodes; and D meansbridging said flanged ends to clamp said flowmeter body therebetween,said means being formed by bolts passing through said flange holes andthe bores in registration therewith.
 2. A flowmeter as set forth inclaim 1, wherein said body further includes a metal ring surroundingsaid pressure vessel.
 3. A flowmeter as set forth in claim 1, whereinsaid vessel is molded about an insulating shell which lines saidpassage.
 4. A flowmeter as set forth in claim 3, wherein said shellincludes a pair of opposed sockets for receiving said electrodes.
 5. Aflowmeter as set forth in claim 4, wherein said shell further includesend flanges.